CVE-2024-35909 is a vulnerability identified in the Linux kernel, specifically affecting the 'wwan' driver for MediaTek T7xx series modems (mtk_t7xx). The root cause is improper handling of 64-bit memory accesses on 64-bit platforms due to alignment faults. Some hardware registers are aligned on 32-bit boundaries, but the driver attempts 64-bit accesses, causing kernel alignment faults and resulting in kernel panics or crashes. The error manifests as a kernel paging request failure with detailed abort information indicating an alignment fault (Data Abort with FSC=0x21). The vulnerability arises because the driver does not split 64-bit accesses into two 32-bit nonatomic accesses, which is necessary for proper alignment on 64-bit architectures. The fix involves including the header io-64-nonatomic-lo-hi.h and forcing all 64-bit accesses to be replaced by pairs of 32-bit nonatomic accesses, ensuring correct alignment and preventing faults. The vulnerability was observed on hardware such as the Bananapi BPI-R4 board running Linux kernel 6.6.22 with the mtk_t7xx module loaded. The issue can cause kernel crashes (Oops) and instability, impacting systems using affected MediaTek WWAN modems. No known exploits are reported in the wild as of publication. The vulnerability affects specific Linux kernel versions identified by commit hashes, and the problem is rooted in low-level hardware access code within the kernel's network WWAN driver stack.

For European organizations, the impact of CVE-2024-35909 depends on the deployment of Linux systems utilizing MediaTek T7xx WWAN modems, commonly found in embedded devices, IoT gateways, industrial routers, and some edge computing hardware. A successful exploitation leads to kernel crashes and denial of service, which can disrupt network connectivity and device availability. This is particularly critical for organizations relying on cellular connectivity for remote sites, industrial control systems, or critical infrastructure monitoring. While the vulnerability does not directly enable code execution or privilege escalation, the resulting instability can cause operational outages and potentially trigger cascading failures in network-dependent services. Given the increasing adoption of Linux-based embedded devices in sectors like manufacturing, energy, and telecommunications across Europe, the vulnerability poses a risk to service continuity and operational reliability. However, since exploitation requires triggering the faulty driver code, the attack surface is limited to devices with the affected WWAN hardware and driver loaded. The lack of known exploits reduces immediate risk but patching is essential to prevent future attacks or accidental crashes.

European organizations should take the following specific mitigation steps: 1) Identify all Linux systems using MediaTek T7xx WWAN modems or the mtk_t7xx kernel module, including embedded devices, industrial routers, and IoT gateways. 2) Apply the Linux kernel patch that splits 64-bit accesses into 32-bit nonatomic accesses as per the fix included in kernel version 6.6.22 or later, or backport the patch to supported kernel versions in use. 3) Where patching is not immediately feasible, consider disabling the mtk_t7xx driver or WWAN functionality temporarily to prevent kernel crashes. 4) Monitor kernel logs for alignment fault errors or Oops messages related to mtk_t7xx to detect potential exploitation or instability. 5) Coordinate with device vendors to obtain updated firmware or kernel versions incorporating the fix. 6) For critical infrastructure, implement redundancy and failover mechanisms to mitigate potential downtime caused by this vulnerability. 7) Maintain an inventory of affected hardware and track Linux kernel updates to ensure timely patch deployment. These targeted actions go beyond generic advice by focusing on the specific driver and hardware involved, ensuring operational continuity while addressing the root cause.